Why do economic agents conform with existing institutions? Drawing on economics and organizational institutionalism, this article identifies existing explanations, extends or refines some of them, suggests new ones, classifies these various explanations, and integrates them into an organized framework. One set of explanations focuses on conformity out of habit. The other refers to more conscious thought and behavior and considers coordination and increasing returns to adoption, social sanctions, informational differences, uncertainty, legitimacy, naturality, and lack of power/resources to deviate.